080717 Phoenix rasps frozen layer and scoops sample

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Phoenix rasps frozen layer and scoops sample
BY DR EMILY BALDWIN
ASTRONOMY NOW

Posted: July 17, 2008

Using the robotic arm’s powered rasp, Phoenix has successfully drilled into the cement-hard frozen soil at its landing site, loosening material that was later collected by the lander's scoop.

Over the last few days Phoenix has been clearing away loose soil from a subsurface layer of hard-frozen material within the Snow White trench that has been the focus of the mission so far. The motorised rasp tool then made two distinct holes in the trench, about one centimetre apart, which loosened the surrounding material.

The rasping tool on Phoenix drilled two holes (upper left and inset) into the cement-hard icy surface in the Snow White trench. Image: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

The rasping apparatus, which is located on the back of the robotic arm scoop, is operated by a motor which rapidly rotates the tool. The angle of the rasp is gradually increased from its near horizontal starting position while it is rotating, so that shavings of the icy surface are kicked sideways onto a collection surface. After the rasp is stopped, a series of moves by the scoop then shifts the collected shavings from the back to the front of the scoop.

"While Phoenix was in development, we added the rasp to the robotic arm design specifically to grind into very hard surface ice," says Barry Goldstein, Phoenix project manager at NASA's Jet Propulsion Laboratory. "This is the exactly the situation we find we are facing on Mars, so we believe we have the right tool for the job. Honeybee Robotics in New York City did a heroic job of designing and delivering the rasp on a very short schedule."

The Robotic Arm Camera documented the chain of events but the images and data sent back to Earth yesterday suggest that the properties of the icy shavings changed slightly over the hours following its collection.

"This was a trial that went really well," says Richard Morris, a Phoenix science team member from NASA's Johnson Space Centre, Houston. "While the putative ice sublimed out of the shavings over several hours, this shows us there will be a good chance ice will remain in a sample for delivery [to Phoenix's laboratory ovens]”.

Members of NASA Phoenix Mars Mission's Robotic Arm engineering team test the arm's motorised rasp in the Payload Interoperability Testbed at the University of Arizona, Tucson. The testbed has a near-duplicate of the Phoenix lander for use in developing techniques to be used on Mars and for checking commands planned for the lander. Image: University of Arizona.

Phoenix will continue to test the rasping method and scooping action under the watchful eye of the lander’s cameras over the next few days, in preparation of collecting and delivering a sample for analysis in one of Phoenix's Thermal and Evolved-Gas Analyser ovens. The Phoenix team has also been testing the rasping and collection techniques on simulated Martian ice with a near-replica model of Phoenix in a test facility at the University of Arizona in Tucson.